Al0.68Sc0.32N Lamb wave resonators with electromechanical coupling coefficients near 10.28%

Abstract

Aluminum scandium nitride (Al1−xScxN/AlScN) (x = 0.32) Lamb wave resonators (LWR) have been fabricated and tested to demonstrate electromechanical coupling coefficients (kt2) in excess of 10%. The resonators exhibited an average kt2 and unloaded quality factor (Qu) of 10.28% and 711, respectively, when calculated from the measured data. Applying the Butterworth Van-Dyke (BVD) model to the measured data enabled the extraction of the resonator's lumped element parameters to calculate the motional quality factor (Qm), which neglects the contributions of the electrical traces. For the best measured resonator response, results from the BVD model showed a Qm of 1184 and a resulting figure-of-merit (FOM = K2 · Qm) of 100. Comparing the response of similar AlScN and AlN resonators shows that the AlScN LWR has a significantly lower motional resistance (Rm), suggesting that AlScN has a strong potential for use in piezoelectric microelectromechanical oscillators.